Ostriches are a large flightless african bird with solid bones and very powerful hindlegs for running and kicking. rheas are from south america. other than the fact that they are about half the size of an ostrich, their physical features are almost identical to ostriches. which conclusion is not supported by the observations concerning ostriches and rheas?
a) ostriches and rheas are probably close relatives, since their features are very similar.
b) ostriches and rheas may have evolved from a common ancestor, since they have so many similar features.
c) the similarity of ostriches and rheas suggests that africa and south america may have been joined at one time.
d) ostriches and rheas started off as different species, but have evolved over time to become identical to each other.

The correct answer is D) Ostriches and rheas started off as different species, but have evolved over time to become identical to each other.

Explanation:

Genetical and phenotypical similarities occur in the case different organisms are related, this implies if two species of birds like rheas and ostriches share many visible traits (phenotype), it is likely these are related genetically and therefore these are the result of evolution from a common ancestor. This occurs because according to the evolution theory, species we know today are the result of speciation in which one ancestral species leads to multiple species due to changes in the environment and other natural phenomena, this makes the species share similarities with related species.

However, this does not suggest "Ostriches and rheas started off as different species, but have evolved over time to become identical to each other" because as previously mentioned the most common path in evolution is for a species to derive into other similar species and common traits are an evidence of this, rather than for two separate species to become identical over time even if they are not related.

1. glaciers are melting

2. more water going into ocean (water's such as fresh waters, etc)

the african cheetah.

this species has a relatively low level of genetic

variation because the population was reduced to a small size approxi-

mately 10,000 to 12,000 years ago.

chapter   outline

24.1

genes in populations and the hardy-

weinberg equation

24.2

factors that change allele and genotype

frequencies in populations

24.3     sources of new genetic variation

population   genetics

24

until   now,   we   have   primarily   focused   our   attention   on   genes  

within   individuals   and   their   related   family   members.   in   this  

chapter   and   chapters   25   and   26   ,   we   turn   to   the   study   of   genes   in  

a   population   or   species.   the   field   of

population   genetics

  is   con-

cerned   with   changes   in   genetic   variation   within   a   group   of   indi-

viduals   over   time.   population   geneticists   want   to   know   the   extent  

of   genetic   variation   within   populations,   why   it   exists,   and   how   it  

changes   over   the   course   of   many   generations.   the   field   of   popu-

lation   genetics   emerged   as   a   branch   of   genetics   in   the   1920s   and  

1930s.   its   mathematical   foundations   were   developed   by   theoreti-

cians   who   extended   the   principles   of   gregor   mendel   and   charles  

darwin   by   deriving   formulas   to   explain   the   occurrence   of   geno-

types   within   populations.   these   foundations   can   be   largely   attrib-

uted to three scientists: sir ronald fisher, sewall wright, and j. b. s.

haldane.   as   we   will   see,   support   for   their   mathematical   theories  

was provided by several researchers who analyzed the genetic com-

position   of   natural   and   experimental   populations.   more   recently,  

population   geneticists   have   used   techniques   to   probe   genetic  

variation   at   the   molecular   level.   in   addition,   staggering   advances  

in   computer   technology   have   aided   population   geneticists   in   the  

analysis   of   their   genetic   theories   and   data.   in   this   chapter,   we   will  

explore   the   genetic   variation   that   occurs   in   populations   and   con-

sider   the   reasons   why   the   genetic   composition   of   populations   may  

change over the course of several generations